1. Field of the Disclosure
The present disclosure is generally directed to drum-type storage containers and more particularly to a split ring clamp or lock ring for securing a lid to such a container, the ring having an integral one-piece molded construction.
2. Description of Related Art
Cylindrical containers or drum containers are known in the art for holding and storing chemicals, industrial materials, and the like. These types of containers are typically large drum sizes and are often constructed of either a metal material such as steel or, particularly in North America, a fiber material. Fiber drums are formed having a metal chime around the top lip or top opening as well as around the closed bottom. In other regions, particularly in Europe and the Far East, such drum containers are often formed of non-metallic and non-fibrous materials, such as plastic materials. With the rapid globalization of commerce, it has become much more common that plastic material is used for fabricating these types of drums, as well as for fabricating their removable lids. In this regard, there are ecological and other advantages associated with use of plastic drums and lids, such as the material being recoverable or recyclable.
Each container of this type has a replaceable lid retained in position by a split ring clamp or lock ring in order to securely close the top opening. International standards are developing, which may supplant separate national standards to regulate the performance of these types of drums and lids. From a national standpoint, the United States Department of Transportation (DOT), Research and Special Programs Administration, has produced standards and specifications for drum performance. Standards also have been promulgated by the United Nations organization. DOT standards typically call for drop tests to make sure the drums won't leak when subjected to some abuse or trauma during use.
The drums to be tested are filled with dry, finely powdered material to a specific net weight. The drums are then closed with the lids and then clamped by the split ring or lock ring. Depending upon the standards involved, the containers are required to withstand a drop from varying heights and at various orientations onto a hard surface such as concrete. To pass such tests or meet the standards, the drums must recover from such drops without rupture or leakage. One international testing approach involves a similar drop test, except that the drums are filled with water instead of powdered materials. Such tests also include a seal test where the drums are filled with water and upended to determine the presence of a leak.
The lids that typically close these types of drums are formed from stamped metal or molded plastic. The lids are then secured onto the drums by the split ring clamps or lock rings. Such clamps or lock rings have a channel to capture a rim of the lid-to-drum interface. An over-center lever is generally used to draw the ends of the split ring clamp structure together. In the past, these lock rings or clamps were made of steel and were durable and sturdy, but heavy and expensive. However, for many packaging, transportation, and incinerator container applications, industrial users of such drum containers have sought to avoid metal components such as lids and lock rings or split ring clamping devices. The known metal devices do not burn, are prone to corrode, and can sometimes insert minute metallic contaminants with the material packaged within the containers.
Plastic lids have been successfully developed, such as is described in U.S. Pat. No. 4,718,571. For some period of time, the development of corresponding plastic clamping rings, which could remain competitive in terms of cost and clamping performance, eluded those in the art until a successful all-plastic polymeric two-piece split ring clamp was devised. Such a plastic clamp ring found success in conjunction with fiber type drums, and is described in U.S. Pat. No. 5,129,537.
The two-piece polymeric split ring clamp described in the above noted '537 patent has remained popular for use with fiber-based drums. However, its experimental application for clamping plastic lids on plastic drums demonstrated a need for a more secure union between drum and lid. Plastic drums and lids typically are less rigid or study than metal drums, fiber drums with steel chimes, and metal lids. Further, the plastic split ring clamp, while advantageously being formed of only two major parts, had exhibited a profile at its over-center pivot level that protruded outwardly a substantial amount from the side of the drum and lid to which it is secured. Such a large protruding ring portion can significantly hinder drum handling. Also, when containers employing plastic lids and plastic drums are subjected to drop tests, excessive stress was imposed, for example, upon the lever pivot shaft or pin that was integrally formed upon the pivot arm of the clamping system.
U.S. Pat. No. 5,713,482 disclosed a split ring clamp or lock ring that provided a degree of improved performance in these areas. However, the ring disclosed in the '482 patent still was made from two separate parts including the split ring and the over-center lever, as well as the parts to attach the lever to the ring. The two parts must be separately fabricated from two different molds and then assembled afterwards in a separate process. The pivot joint of the over-center lever is also still subjected to a large amount of stress when securing the lock ring or clamp onto a drum and lid assembly and after being secured.